Trunking system of radiodistribution



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E.E.CLEMENT TRUNKING SYSTEM OF RADIODISTRIBUTION Original Filed Jan. 21 19 5 5 Sheets-Sheet 5 ""2 neomwu Patented Mar. 16, 1926.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD I". COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

TRUNKING SYSTEM OF RADIODISTRIBUTION.

Application filed January 21, 1925, Serial No. 3,861. Renewed February 11, 1926.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at \Vashington, in the District of Columbia, have invented certain new and useful Improvements in Trunking Systems of Radiodistribution, of which the following is a specification, reference being bad therein to the accompanying drawings.

The present invention is a continuation in part of my copending application Serial No. 754,406, filed December 6, 1924; it relates to systems of radio broadcast distribution, and has for its object to organize such a system so that a program may be originated relayed and distributed over a large area, uniformly and in a systematic and orderly manner to authorized users or subscribers who will get the full benefit of the use of vacuum tubes in receiving and amplifying without the necessity of maintaining tubes at their stations,

, the tubes used by the subscribers in receiving being located at central points where supervision maintenance power supply and control may be centralized and put under the care of expert operators.

In the prior application above referred to, both relay distribution and supervision of the broadcast service for a group of subscribers is carried on at the central station or exchange local to the group. The subject of the present application differs from the aforesaid in that a district relay station, common to several subscribers central stations, is provided for distributing broadcast matter to the central stations by radio, the central stations distributing the broadcast matter to their respective subscribers by wire, while supervision of the reception at the central stations is had at the district relay station over individual telephone lines and trunks connecting the district relay station with the different central or local distributing stations.

The invention is applicable to manual automatic or so-callcd semiautomatic or autoinanual telephone systems, the principles involved not being changed by different methods of efiecting or controlling the necessary electrical switching connections. My invention is illustrated in the accompanying drawings, in which:

Figs. 1 and 2 indicate diagrammatically,

'the telephone exchange portion and the broadcast distributing portion of a subscribprs central station forming part of my sys- Fig. 3 is a diagrammatic representation of a district studio and radio relay station.

Fig. 4 is a schematic diagram showing the system as applied to a district containing several local or exchange groups.

Fig. 5 is a diagram showing an arrangement of circuits and apparatus aifording selection of a plurality of programs.

Referring to the drawings in detail and first to Fig. 1, this shows the essential circuits of an ordinary telephone exchange system in which JJ are line terminal jacks forming the terminals of telephone lines leading to stations to be interconnected such as the subscribers station A. These jacks are arranged to be interconnected through the usual answering and calling plugs P-P' forming the terminals of the usual common battery cord circuit, shown. The central office terminals of each line are provided with the usual line relay L line lamp L? and cut-off relay L Where service is to be metered a recording meter M is also individually associated with the line. Thus, the circuit arrangement here shown is that of the standard multiple switchboard, common battery, telephone exchange system, and as such is well understood in the art further detailed description thereof will be here deferred and brought out later in the description of operation. In addition to the usual line terminal, multiples 1, 2 and 3, representing multiples of the tip, sleeve and test or cut-off circuits, respectively, I provide a fourth conductor 4 leading from a contact on the line relay along with the multiple conductors 1, 2 and 3 to the broadcast distributing system diagrammed in Fig. 2.

Fig. 2 shows the broadcast distributing system of which the portion to the left of the dotted line is situated at the central ofiice and connected with the subscribers telephone line terminal apparatus of the telephone central C (Fig. 1) through conductors 1, 2, 3 and 4, while the portion to the right of the dotted line in Fig. 2 is situated at the subscribers substation and connected with the subscribers telephone substation apparatus A (Fig. 1) through the multiple conductors 5 and 6. In Fig. 2 the subscribers line multiples 1-2 terminate in the spring contacts 78 of a jack 9 which contacts are arranged upon the insertion of the dummy plug 10 to be spread apart to engage with the stationary contacts 1112 to extend the connection of the multiples 12 to conductors 21-14. The conductor 13 connects with the positive terminal of the common central ofiice battery B through the winding 15 of a repeating coil 19 while the conductor 14 connects with the negative terminal of the battery 3 through a sleeve or supervisory relay 42 and the winding 16 of a repeating coil 20. An audion tube 37, individual to the line, is also provided which is arranged with its output or plate circuit conductors 21-22 connected in series with the windings 17 and 18 of the repeating coils 19 and 20 and a plate battery B. The input circuit of the tube 37 is arranged to be connected through contacts 23-24 on the supervisory relay 42 and conductors 25-26 to the program busses 27 -28 to which are connected the audio output terminals of the radio receiver or broadcast relay and distributer 29 which may be of any known or other suitable type of radio receiver capable of furnishing the bosses 27-28 with audio signaling currents of suflicient strength to supply the input circuits of the several subscribers line tubes 37, it being understood that several such line tubes (not shown) are supplied from the common busses as indicated by the multiple branch conductors 30. A normally closed contact 31 on the relay 42 connects the common battery 13 to the conductor which-terminates in a normally open contact 33 in the jack 9 operable to extend the connection of conductor 32 to the signaling conductor 4 to supply battery potential thereto. This signal conductor is arranged to be connected with battery upon energization of the subscribers line relay through the line relay contact 52, Fig. 1. The relay 42, Fig. 2, also controls the connection of the multiple test circuit conductor 3 to the common battery B through a normally open contact 34 which connection includes a special tone test device of any known or other suitable form, indicated diagrammatically at 35, operable to superpose a characteristic signal current on the test conductor 3. Connected between the signal conductor 4 and ground is a signal lamp 36 mounted near the jack 9 in the manner of the usual telephone line or call lamp.

In Fig. 3, which shows the equipment at the district or relay station, the radio relay apparatus indicated diagrammatically at 39 my be of any known or other suitable form operable to receive radio broadcast matter from one or more distant stations and relay the same to the several subscribers central distributing stations like that of Fig. 2. These district stations are preferably also provided w th means for origlnating broadcast matter, for example, a microphone 40 and modulator 41 connected with the relay apparatus.

A telephone trunk 101102 connects the district station Fig. 3, with the central station Figs. 1 and 2, which trunk terminates in a jack 38 at the district station, Fig. 3, and in the usual line terminal apparatus 43 at the central station Fig. 1, which line terminal apparatus is the same in all respects as that of the subscriber A. This terminal apparatus, like that of the substation A is provided with multiple conductors 221, 222, 223 and a signaling conductor 224 corresponding in function to the conductors 1, 2, 3 and 4 respectively, of the substation A, leading to broadcast line terminal equipment not shown but similar in all respects to that shown in Fig. 1 associated with the line terminals of the substation A.

Other jacks 44 and 45 at the district station form the terminals of other telephone trunks 201202 and 301302 connecting with other central stations like that of Figs. 1 and 2. Any of the lines 101-102, 201-202, etc. may be connected with the supervisory telephone set 46 through the plug 47' and the respective line jacks 38, 44, etc. Any of the lines 101-102, etc. may be also operatively connected with the modulator 41 through the plug 48 and their associated line jacks 38, etc. To effect other combinations of connections between the jacks 38, etc. the modulator 41 and telephone set 46, the said jacks are connected with multiple jacks 138, etc., and connecting cords or link circuits such as 49 provided for connecting one or more lines to either or both the modulator and telephone set.

In addition to the ordinary telephone lines 101-102, etc., the district station is connected with the broadcast distributing portion, (Fig. 2) of the central station through a pair of test circuits comprising a test trunk 150-151 and an order circuit 152153. The test trunk is a simple normally disconnected two wire circuit terminating at both ends in simple jacks 50 and 51. The order circuit 152153 terminates at the district station in a jack 72 and at the central station in a jack 73 and the usual common battery line terminal apparatus 54 with line lamp 55, the jacks 51, 73 and lamp 54 being located before an operator at the central station equipped with means for communicating with an operator at the district station which means may be an ordinary common battery cord circuit indicated symbolically at 56 (Fig. 2) and means for connecting the test trunk with the broadcast busses 27-28, which latter means is here shown as a simple plug and cord, link circuit 57 for connecting the jack 51 with a jack'58 connected with the bosses 2728. At the district station, Fig. 3, an operators testing apparatus 59 is arranged to be connected with the test trunk through a plug 80 and the jack 50. Other pairs of test trunks and order circuits 161-162, 163164, etc. extend from the district station to other central stations equipped like that of Figs. 1 and 2, said trunks and order circuits termi nating at the district station in jacks 81, 83, etc. situated with the jacks 50, 72. before the test operator and accessible to the plug 80. To enable tests to be made of a relay apparatus at the central oflice with all lines disconnected therefrom but without interrupting the service, the central oflice may be provided with a duplicate relay apparatus 89 arranged to be connected to the busses 2728 by closure of a switch when the apparatus 29 is disconnected by opening the switch 71, for test purposes.

Before proceeding with the description of operation of the system a broader view of the. system is advantageous and may be had by reference to Fig. 4 wherein the district station 38 is indicated as being operatively associated with several local groups or subscribers distributing centers 91, 92 and 93, each equipped as indicated in Figs. 1 and 2. The district station is arranged to receive broadcast matter from any distant station and relay the same by radio to the several subscribers distributing central stations 490, etc. as indicated by the arrows adjacent to the antenna symbols on the several stations. The station 490 represents the station diagrammed in Figs. 1 and 2 while the substation A' represents the station A of Figs. 1 and 2. Also the various lines and trunks 69-70, 150151, 152153, etc. represent those correspondingly numbered in Figs. 1, 2 and 3.

In operation, broadcast matter is trans mitted from the district station (Fig. 3) by radio to the relay apparatus at the different central stations such as the relay and distributor '29 (Fig. 2), the audio output circuit of which is connected through switch 71 to the busses 2728. A subscriber at substation A desiring broadcast service, now connects his broadcast receiving or extension set A to the line by inserting the receiver plug 1 in the jack J which connects his receiver 64 across the line multiples 5 and 6 through the booster coil windings 6065 and condenser 66 in series, and closes a path for direct current between the multiples 5 and 6 through coil 60, lower spring of jack J. transmitter 62 and signaling key 63.

This energizes the subscribers line relay at the central oflice in the usual manner by current from the central otfice, common battery B. conductor 68, right hand winding of relay L, line conductor 69, to subscribers substation A, line multiple 5, to subscribers broadcast receiving set A (Fig. 2), coil 60, t ansm ter 62. contacts of key conductor 6, 70, left hand winding of line relay L and back to battery B. Actuation of the line relay energizes the line lamp L by closure of a local circuit which may be traced from common battery B through circuit elements L 71, 68, and back to battery B. This causes the line lamp L at the telephone operators switchboard to glow, but only for a moment, as the subscriber wanting broadcast service will immediately operate his signal key 63 to rapidly open and close his line circuit which causes his line lamp to flicker instead of glowing steadily and so indicate to the telephone operator (Fig. 1) that the subscriber is not calling for. a telephone connection. This intermittent actuation of the subscribers telephone line relay L also causes a flickering of the lamp 36 (Fig. 2) associated with his broadcast service, multiple jack 9 situated before the broadcast serv- 1ce operator. This operator perceiving the flickering of the lamp interprets the signal as a call for broadcast service and in answer thereto inserts the actuating plug 10 in the 'ack 9. This effects the closure of contacts -11, 812, and 33. Closure of the contacts 7-11, 812, connects the battery B (Fig. 2) across the subscribers line through the repeating coil windings 15-16 and the sleeve supervisory relay 42 which connection may be traced from battery B (Fig. 2) through circuit elements 15, 13, 11, 7, 1, (into Fig. 1 69, 5, (into Fig. 2), 60, 62, 6, (into Fig. 1 7 O, 2, (into Fig. 2) 812, 14, 42, 16, back to battery B. As this completes the circuit including the battery B "and the relay 42, this relay is ener 'zed and closes the circuit of the cut-off re ay L (Fig. 1) over a path which may be traced from the common battery B (Fig. 2) through the circuit elements 35, 34, 3, (into Fig. 1), cut-off relay L 68, and through ground back to common battery B. Energization of the cutoff relay disconnects the subscribers line from the telephone line signal apparatus in the usual manner, thus causing the line lamp L to become deenergized and extinguishing both signal lamps L and 36. As the cut-01f relay is held energized over the test conductor 3 by battery supplied thereto through the special tone test device 35, a telephone operator in testing the line will receive this characteristic tone test instead of the usual click in the ear indicating that the subscribers line is busy with the special or broadcast service which may or may not be interrupted for telephone service according to the wishes of the subscriber. Energizetion of the relay 42 (Fig. 2) also connects the input circuit of the subscribers line tube 37 to the broadcast busses 2728 by way of contacts 23, 24 and conductors 25, 26, respectively. The actuation of relay 42 also energizes the subscribers line lamp 37 by closure of its filament circuits through contact 351, and filament battery F. The plate circuit of the tube 37 is energized from battery B through the plate circuit conductors 21, 22. and repeating coil windings 17 and 18. Thus the broadcast matter supplied to the input circuit of the tube 37 from the busses 2728 is amplified in the output circuit 22, 18, B, 17, 21, and transferred into the subscribers line circuit by the repeating coil windings 15-16 included in the line circuit. The broadcast signal currents passing through the winding 60 of the booster coil (31 are repeated in the coil and included in circuit with the subscribers broadcast telephone receiver 64 which circuit may be traced from the coil (35 through circuit elements J", P 64, P J 89, 62, 63, 266, back to coil 65.

\Vheu the subscriber desires to discontinue the use of the broadcast service, the plug P (Fig. 2) is pulled which opens the line circuit at the jack 9 deenergizing the relay 42, which in turn connects the battery to the signal circuit conductor 4 through relay contact 31 and energizes the radio service signal lamp 36 over a circuit which may be traced from common battery B through circuit elements 31, 32, 33, 4, 36 to ground and back to common battery B. This causes the lamp 36 to glow steadily indicating to the broadcast service operator that a disconnection is desired whereupon the operator pulls the plug 10 which opens all the contacts of jack 9 and restores the circuits to normal.

\Yhen it is desired to originate broadcast matter at the district station (Fig. 3), microphone -1O is used which operates through a modulator and transmitting portion of the radio relay 39, the circuits and apparatus of which modulator and transmitting portion of the relay being of any known or other suitable type. \Vherc it is desired to permit a subscriber to broadcast from his substation he may be connected through the ordinary telephone exchange circuit (Fig. 1) to the telephone line circuit 101102 terminat- 'ing in the multiple jacks 38 and 138 at the district station (Fig. 3) from which the connection may be extended by plug 48 to the modulator of the relay transmitter 39. To enable the operator at the district station to listen in on the broadcasting subscribers line. the listening set 46 may be connected to the line through the plug 47 and the remaining one of the multiple jacks 38 and 138.

A test of the quality of reception at the central station (Fig. 2) may be had from the district station (Fig. 3) over the testing trunk 150151 through the jack and the plug connection 50 and 47, and the listening set t6. the testing trunk having been connected with the output of the receiver 29 (Fig. 2) through jacks 51 and 72, and the link circuit 57, it is desired that this test he made on the output of the receiver 29 free of all subscribers line connections, a duplicate relay transmitting apparatus 89 may be ut into service and connected to the distributing busses by closure of switch 70 before opening the switch 71 to clear the apparatus 29, thus preventing interruption of the broadcast service. Other tests of the output circuit or other portions of the apparatus at the central station may be made 75 over the test trunk by connecting the operators testing apparatus 59 (Fig. 3) through the plug and jack 50 to the test trunk, it be'ng understood that the apparatus 59 may consists of suitable testing or measuring in- 80 struments such as a source or sources of current, ammcters, voltmeters, etc. In making these tests, the operator at the district station makes use of his listening set 46 and the order circuit 152153 to communicate 35 program bus 2728 with single line switches or jacks 9 at the central distributing stations. It is of course obvious that these elements may be multiplied, that is to say, that the relay distributing station shown in Fig.

3 may be equipped to receive simultaneously from several sending stations, or may be equipped to receive from one or more sending stations and simultaneously to originate matter for distribution among the several district central stations shown in Fig. 2.

Each central station would then have a number of receiving instruments 29, adapted to receive the different programs, and the output of each of these receiving instruments would be communicated to a separate trunk so that there would be a number of program trunks similar to that shown in Fig. 2 at 2728, to any of which the subscribers may have access. For this purpose, the switching apparatus disclosed in my two prior 00- pending applications, Serial No. 754,406, filed December 6, 1924, and Serial No. 913, filed January 6, 1925 may be employed. A simple form of selective apparatus working in conjunction with the line switch 9 is shown herein in Fig. 5. In the arrangement of this figure, the subscriber calls as before giving one long closure for a telephone call, and a series of short flashes for a radio call.

This may be done by means of a key 63 (Fig. 2) or the ordinary automatic sender well known to those skilled in the telephone art. At the telephone station A of Fig. 1, it is unnecessary to have any key or keys to secure telephone connection, it is only neces- 89 sary to remove the receiver from the switchhook as usual, this producing a continuous make, as at present. 7

Referring to Fig. 5, the parts are exactly as in Fig. 2, with the exception that a selective switch S is provided, stepped around by means of an electromagnet 420, controlled through front contacts 310 by the relay 42 which is included in the line circuit of battery B when the contacts of the line switch 9 are closed by the radio operator. The selective switch S contains bank contacts ss's connected to separate busses 27-28 (carrying No. 1 program), 270280 (carrying N0. 2 program), and 2700-2800 (carrying No. 0 or announcements). The switch S does not need to be restored to zero, and may be left always in the last position to which it has been moved, since the wires 25-26 leading to the wiper arms 8 of the switch are cut off at the relay contacts 2324 when the apparatus is in disuse. The No. 1 and No. 2 program busses are connected to the output circuits of broadcast relay receivers 29-290 respectively, and the announcement bus 27002800 is connected to a local distributing apparatus or amplifier with a microphone M7. The announcement set as a whole is connected symbolically only at AS. This position or equipment on the radio switchboard corres onds to the information operators positlon on a telephone switchboard.

The operation of Fig. 5 is as follows: The subscriber calls as before, by making short closures of his line at the key 63, after inserting the plu P in the jack J These short closures ash both the telephone and the radio switchboard lamps L (Fig. 1) and 36 (Fig. 2). Connection is established by the radio operator inserting the plug 10 in the jack 9, or closing the equivalent switch. It may be mentioned in passin that any form of switch may be substitute for the jack 9, even to a relay controlled from a keyboard position by the operator, without departing from the invention. Divers forms of switches suitable for this purpose will occur to those skilled in the art, such as for example, a key switch of the general type of operator s ringing and listening key, having pivoted lever and a rocking wedge passmg up and clown between the pairs of contact springs, to open and close them. Such a switch may have practically any desired number of contacts, and requires no separate plug to operate it. The additional contacts are available for a number of purposes, including the cut-off of battery current from the magnet 420 when the parts are in disuse, which should be done as a matter of good practice, although not necessarily a part of the invention.

The subscribers line having been thus connected with the central office wires 1-2,

the relay 42 is included therein, and comes under the control of the subscriber. Since his line circuit remains closed after signaling at the key 63, the relay 42 is energized,

and closes all its contacts 310, 34, 24, 23 and 351. This connects the input or grid side of the line tube 37 to the switch wipers s and also closes the filament circuit through battery F. The three pairs of bank contacts s--ss represent a suitable number If it is a program bus and he desires to select some particular item, he can by means of his key 63 propel the switch arms 8 until they come in contact with the bank contacts 8 connected to the announcers bus 270() 2800, and by listening, he will hear a continuous announcement of the items then upon the bus, the items to follow, the numbers or call letters of the stations from which the said items are being sent, and any other interesting information connected with the same. I consider this separate announcement bus, corresponding to an information operators position, to be important as well as novel and original with myself, and shall claim the same accordingly. Having ascertained what program and what items he desires to hear, the subscriber is able to start from zero and step the switch around to the desired busses such as 27-28, 270-280, etc.

Thus the announeers bus, when reached,

which is always easily distinguishable, serves a double purpose, being also the zero bus from which the program busses are counted. If the subscriber has a loud speaker, and desires some particular item for which he has to wait, he may leave his switch connected with the announcers bus until the time for making connection arrives, and in the meantime will receive all the announcements, with such matters of entertainments and information as may be intercalated therebetween. This means that during the entire broadcasting period, the announcements will be going on, interspersed with comments, explanations, etc.

The switch so erated in the usual manner. For metering the radio service, I have shown in Fig. 2 the commutator and high voltage generator adapted to meter operation, in a manner familiar to those skilled in the art. This generator is only connected when the relay 42 is energized and the commutator closes the circuit, which occurs at intervals during the time the subscribers line is connected to the radio bus or busses. I have also shown a meter operating generator and commutator in Fig. 5, but it is to be understood that in the latter case, where there is selection of program, there should also be selection of a charging rate corresponding thereto; which means that there would be a separate meter commutator for each of the program busses, brought into connection with the contacts 34 and test wire 3 through bank contacts of the switch S, corresponding to the program contacts 8-8'-8 associated therewith. B adjusting these separate commutators to di 'ferent speeds or rates of operation, the metering can be made variable, according to the program being received. This, is described and claimed in my prior copending applications, Serial No. 746,357, filed October 28, 1924, and Serial No. 746,358, filed October 28, 1924. Any method of differential metering may be employed for this purpose without departing from the scope of my invention.

It should be stated in closing that While I have developed herein a specific arrangement of the apparatus and circuits for the purposes stated, there are a number of modifications which I contemplate and shall not describe herein specifically, because they will form the sub'ect matter of separate applications. I wis to state herein however, that according to one modification, the line signal lamp 36 on the radio switchboard, and the line vacuum tube 37 on the same, may be and preferably are made one and the same unit. The tubes 37 are used as amplifiers, which means that they will be lighted -to somewhat reater brilliancy than if used as detectors, ence under proper conditions of lighting and arrangement, they may very well be used for visible signals. According to this arran ement, when a subscriber calls radio, he wil flash the filament of the tube 37, which gives the visible signal to the radio operator that he desires radio connection. The tube 37 for such use would be located in a designated and determinate position to indicate the identity of the line, and would preferably be associated with the line switch 9. When the plug is in or throws the switch 9, the result would be to cut off the direct line connection with the tube 37, and substitute the working circuits through the tubes as shown in Fig. 5. In clearing out the subscriber may then again flash the filament of the tube 37, which with the switch 9 closed, would indicate disconnection.

An advantage of using vacuum tubes for the signal lamps lies in this, that by flashin the filament, if the grid circuit be close thereby, an audible signal can be produced in the plate circuit. It may of course be provided that when the switch 9 is in disuse and its contacts open, the subscriber in calling would close the filament and grid circuit through a buzzer or other audible signal, and in such case a receiver in the plate circuit would give out the sound. The most practical use of this would be to energize a position or section signal, common to the number of lines, to call the operators attention to the call for connection or disconnection, as the case may be.

W'hile I have herein described and illustrated the use of audio frequencies for distribution to the subscribers over their wired line circuits the invention is not limited to such frequencies but may employ also superaudio frequencies, so long as they are suitable for line transmission. In the work heretofore done by Major General Squier and others, frequencies ranging from 25 to 100 kilocycles per second have been found suitable for this purpose. In order to make such frequencies available for distribution among the subscribers in the present system, the connections from the central station receiving and relay distributing apparatus remain practicall the same, as those described and shown in igs 2 and 5, the input or grid circuit of the individual line tube 37 also remaining the same. The repeating coil connection to each line must either be supplemented or replaced however by a filter connection, preferabl ermanent, which will permit superaudio frequency currents to be transmitted from the plate circuit of the tube to and over the line circuit to the subscribers station, while the battery current from the battery B will simultaneously flow over the subscriber's line for signaling and talking purposes of the subscriber. At the subscribers station, complementary connections must be made, and a detector radio set must be connected to receive superaudio currents over the line, while the telephone elements are connected, preferably in parallel, to receive the battery current and transmit and receive audio frequency waves. Such an arrangement is shown as to its principles in Letters Patent granted me January 6, 1925, No. 1,552,362, to which reference is had for further explanation of the principles involved.

I do not claim the method of selection of program or the switching circuits and apparatus therefor, as described herein, the same being the subject of my divisional apswe t-3st? plication, Serial No. 89,411, filed February 19, 1926.

lVhat I claim is: v

1. In a system of radio broadcast distribution, a district broadcast service station, a plurality of telephone central stations each with subscribers substations and Wire lines interconnecting them, radio broadcast transmitting means at the district station, distributing relay means at each central station for relaying the matter broadcasted from the district station onto distributing conductors at the central station at a frequency suitable for transmission over subscribers wire lines, relay means at each central station individual to each subscribers line, and means also at each central station for connecting a subscribers line through its associated relay means to the said distributing conductors at that central station.

2. The system claimed in claim 1 with means for individually communicating, between the district station and said central stations.

3. The system claimed in claim l'with wire lines connecting the district station with said central stations.

4. The system claimed in claim 1 with test. circuit trunks connecting the district station with central stations and an order circuit trunk associated with each said test circuit trunk.

5. In a system of radio broadcast distribution, a plurality of subscribers stations divided into a plurality of groups, a "55 connected to an one of saiibgssgs district radio broadcast station common to said groups, a central station for each group having receiving means for receiving the broadcast from said common district station, 40

and individual amplifying relay means arranged to connect each subscribers station with the receiving means at the central station of its group.

6. In a system of radio broadcast distribution, a plurality of subscribers stations divided into a plurality of groups, a. district radio broadcast station common to said groups, a central station for each group having receiving means for receiving the broadcast from said common district station, and individual amplifying relay means arranged to connect each subscribers station with the receiving means at the central station of its group, together with means at the district station for supervising the reception at said central stations.

7. In a system of radio broadcast distribution, a plurality of subscribers" stations divided into a plurality of groups, a district radio broadcast station common to said groups, a central station for each group having receiving means for receiving the broadcast from said common district station, and individual amplifying relay means arranged to connect each subscribers station with .the receiving means at the central station of its group, said district radio broadcast station being equipped to transmit a plurality of programs simultaneously, each group central station having means for distributing them on different busses,

se ective switchin means w ere v it may ,a

and each sub scribers indivi l amphf in re a llaVlllrr n es lmony w ereo I hereunto alfix my signature.

EDWARD E. CLEMENT. 

